Japan has highlighted China's growing assertiveness as a risk to regional tensions in its annual defence report, which analysts said aims to justify Prime Minister Shinzo Abe's push for controversial security legislation.

The Defence White Paper, approved by the Japanese cabinet yesterday, also called on Beijing to stop construction of new oil and gas exploration platforms near disputed waters in the East China Sea claimed by both countries. It said such platforms would aid China's surveillance of Japanese and US naval activities.

China's military and security development has previously featured in the annual report. But this year, the paper said Japan faced an "increasingly severe" security environment in the region and raised concerns over China's activities in the East and South China seas. "China, particularly over maritime issues, continues to act in an assertive manner, including coercive attempts at changing the status quo, and is poised to fulfil its unilateral demands without compromise," the report said.

Other security threats mentioned were North Korea's nuclear ambitions and Islamic extremism.

This year's defence paper was delayed for more than a week because hawkish members of Abe's ruling Liberal Democratic Party insisted on mentioning China's unilateral maritime activities, including oil and gas exploration in the East China Sea.

The 429-page document said China resumed exploration in the East China Sea two years ago and had started construction of new platforms near disputed areas.

Japanese Defence Minister Gen Nakatani said on July 10 that China "could deploy radar systems on the platforms and use them as an operating base for helicopters or drones conducting air patrols".

A Japanese official said platforms were being built on the Chinese side of a median line that Japan uses to delineate the exclusive economic zones of the two countries. China does not recognise the line.

Last week, Japan's powerful lower house of parliament passed security bills that will allow Japan to fight abroad alongside its allies. The legislation, now waiting for upper house approval, has met strong opposition from the Japanese public.

Ni Lexiong of Shanghai University of Political Science and Law, said the report's emphasis on China's threat was an attempt to justify expanding the role of the army. "The government would also hope to convince the public of the need to have a stronger US-Japan alliance," he said.